Hydraulically or pneumatically controllable slide valve arrangement

ABSTRACT

There is disclosed a fluid-operated, in particular a hydraulically or pneumatically controllable slide valve arrangement for alternately communicating in flow relationship an outflow conduit with a pressure conduit and return flow conduit of a fluid-operating system. This slide valve arrangement comprises a slide valve housing equipped with the aforesaid outflow, pressure and return flow conduits, and a sleeve valve or slide valve piston member is disposed in such slide valve housing. A respective coaxially extending displacement piston member acts upon each end face of the sleeve valve member, the effective cross-sectional area of both displacement piston members differing from one another. Additionally, there is provided fluid-operated control circuit means for continually applying a predetermined control pressure of a fluid medium to the displacement piston member possessing the smaller effective cross-sectional area and for alternately applying the control pressure of the fluid medium of the control circuit means and a considerably smaller pressure to the other displacement piston member possessing the larger effective cross-sectional area.

nited States Patent [72] Inventor Eduard Furrer 3,349.800 lO/l967 Herion et all... l37/625.66 Zurich, Switzerland 3 425449 2/1969 Leibfritz .v 137/625.64 [21] Appl. No. 782,936 3 452 779 7/1969 Klessig et al l37/625.66X

gg s g s 3 Primary Examiner-Henry T Klinksiek [73] Assignee Contraves AG. Attorney Werner w Kleeman Zurich, Switzerland a curpol'afim' of Switzerland ABSTRACT: There is disclosed a fluid-operated, in particular P 22s 1967 a hydraulically 0r pneumatically controllable slide valve ar- [33] swltzefland rangement for alternately communicating in flow relationship [31] 1882/67 an outflow conduit with a pressure conduit and return flow conduit of a fluid-operating system. This slide valve arrangemerit comprises a slide valve housing equipped with the 54 1 HYDRAULICALLY OR PNEUMATICALLY g Y s z f: g

CONTROLLABLE SLIDE VALVE ARRANGEMENT 5 F e v P 7 Chi slide valve housmg. A respective coaxially extendmg displacems, 4 Drawing Figs.

ment piston member acts upon each end face of the sleeve [52] US. Cl ..137/625.63, alve member, the effective cross-sectional area f both dis- 137/625-66 placement piston members differing from one another. Addi- [5 l 1 ll.-

tionauy there is provided fluid operated control circuit means Fleld of Search l for continually a predetermined control pressure of a 625-64, 625-66 fluid medium to the displacement piston member possessing 56 the smaller effective cross-sectional area and for alternately 1 Reerences cued applying the control pressure of the fluid medium of the con- UNITED STATES PATENTS trol circuit means and a considerably smaller pressure to the 3,016,065 1/1962 Stampfli l37/625.64 other displacement piston member possessing the larger efiec- 3,219,060 1 1/1965 Pearl et al 137/625 .66X tive cross-sectional area.

6041\11 421 1.544 3230 3 l l l l l l l R12 A13 P14 I L 43 r 31 R r 5 A 0 HYDRAULICALLY ORPNEUMATICALLY CONTROLLABLE SLIDE VALVE ARRANGEMENT OBJ ECT IVE OF THE INVENTION The invention relates to a new and improved fluid-operated, especially hydraulically or pneumatically controllable slide valve arrangement for alternately operably communicating an outflow conduit with a pressure conduit and return flow conduit of fluid-operating system.

It is a primary of the invention to provide an improved fluidoperated slide valve arrangement which effectively and reliably fulfills the aforementioned purpose.

Another, more specific object of the invention relates to an improved hydraulically or pneumatically controllable slide valve arrangement which is relatively simple in construction, economical to manufacture, not readily subject to breakdown, extremely reliable in operation, and requires a minimum of maintenance and servicing.

Now, in order to implement these and still further objects of the invention which will become more readily apparent as the description proceeds, the inventive slide valve arrangement is generally manifested by the features that a respective displacement piston member acts upon each end face of a sleeve valve or piston member of the slide valve arrangement, the displacement piston members extending substantially coaxially with respect to such sleeve valve. Furthermore, the effective crosssectional area of these displacement piston members differ from one another, the displacement piston member having the smaller effective cross-sectional area being continually impacted by a predetermined pressure of a hydraulic or pneumatic control circuit means, whereas the pressure of such control circuit means and a considerably smaller pressure alternately acts upon the other displacement piston member having the larger efiective cross'sectional area.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood and objects other than those set forth above, will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein: I

FIG. I is a schematic longitudinal sectional view of a firs embodiment of the inventive slide valve arrangement;

FIG. 2 is a sectional view showing details of the sleeve valve or piston member used in the slide valve arrangement of FIG.

FIG. 3 illustrates is schematic longitudinal sectional view, as viewed substantially along the lines I-I of FIG. 4, a second embodiment of inventive slide valve arrangement constructed as a two-stage slide valve unit; and

FIG. 4 is a fragmentary cross-sectional view of the two-stage slide valve unit of FIG. 3, viewed substantially along the line II-II thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Describing now the drawings, the exemplary embodiment of inventive slide valve arrangement depicted in FIG. 1 encompasses a slide valve housing I which contains a longitudinally extending main bore or compartment which slidably receives therein'a sleeve valve or slide valve piston member 4. This slide valve housing 1 is further provided with an annular groove II, additionally a return flow conduit or, connection R12, an outflow conduit or connection A13 and a pressure conduit or connection P14. At each end of the housing I there is mounted in fluid-tight or sealing relationship a cover member 2 and 3, respectively, equipped with the bores or channels 20, 21, and 30, 31 respectively. The bores and 30 are different in cross-sectional area from one another and serve as guide means for the displacement piston members 22 and 32, respectively, which also differ in their effective crosssectional area from one another. These displacement piston members act upon the end faces of the sleeve valve 4, as will be explained shortly.

Continuing, sleeve valve 4 possesses two annular grooves 41 and 42 provided at respective regions of the body of the sleeve valve which are reduced in cross section as shown. Furthermore, sleeve valve 4 is internally provided with a longitudinally extending bore or channel 40 having the widened or enlarged bore portions 44 at each end thereof. Moreover, an operation or through passage opening 43 provided at the body of the sleeve valve 4 communicates the axially extending internal bore or channel 40 with the annular groove 41. A respective square member 45, or equivalent structure, is inserted in each widened or enlarged bore portion 44 of the axially extending bore 40. Each associated displacement piston member 22 and 32, respectively, acts upon the corresponding oppositely situated square member 45. I

As best evidenced by referring to FIGS. I and 2, by virtue of the aforementioned construction, there exists a continuous flow communication between the portions of the main compartment or bore 10 disposed to the left and/or right externally of the sleeve valve or piston member 4 and the return flow connection or conduit R12, so that leakage fluid medium flowing away at the displacement piston members 22 and 32, or otherwise out of the pressure system, does not impair the to-and-fro movement of the sleeve valve 4, rather can flow back to the return flow conduit or connection R12.

The aforedescribed slide valve arrangement can be conveniently actuated by a fluid-operated system, in particular a hydraulic or pneumatic system which embodies a conventional pump D, the pressure line P and the return flow line R, as well as a standard reversing valve unit S. This reversing valve unit S serves to selectively operatively communicate the displacement piston member 22 having the larger effective cross-sectional area either with the pressure line P or with the return flow line R. The other displacement piston member 32 is, similar to the pressure conduit or connection P14, coupled with the pressure line P.

In the depicted position of the reversing valve unit S the sleeve valve or slide valve piston member 4 is retained by the displacement piston member 22 is the illustrated position. The outflow or outlet conduit or connection A13 communicates via the'annular groove 41 with the return flow conduit or connection R12. If the displacement piston member 22 is operatively coupled via the reversing valve unit S with the return flow line R, then the displacement piston member 32 displaces the sleeve valve 4 to the left until it impacts against the cover member 2. Consequently, the pressure conduit P14 is operatively connected with the outflow conduit A13 through the agency of the annular groove 42, whereas at the same time the return flow conduit R12 is cutoff from the outflow conduit According to the variant embodiment of slide valve arrangement depicted in FIG. 3, the sleeve valve 4 can be controlled by means of a further sleeve valve or slide valve piston member 5 mounted directly in the slide: valve housing I and, in turn, controlled pneumatically or hydraulically. In this arrangement this control sleeve valve or piston member 5, possessing the annular grooves 51 and 5.2 at the reduced body portions of such sleeve valve, is located in a lengthwise extending bore 50 equipped with the widened chambers or compartments l6 and 17 at each end. Each such widened compartment l6 and 17 is sealed by an associated membrane or diaphragm I20 and 130, respectively. Furthermore, the slide valve housing I is provided with the control connections or ports 24 and 34, as best shown in FIGI3, whereby it is possible to deform the associated membranes I20 and I30, respective ly, by means of a pneumatic or hydraulic fluid medium in such a way that the control sleeve valve 5 can be reciprocated to and fro. 1

In the exemplary embodiment illustrated, the main bore I0 is enlarged by the annular grooves I41 and 142, as shown. Furthermore, the sleeve valve or piston member 4 is provided with a noncontinuous axial bore 430, in other words, a bore which is open at one end, and in which there is situated the displacement piston member 432. Displacement piston member 432 continuously remains in operable communication with the pressure conduit or connection P14 through the agency of the annular grooves 42 and 142 as well as the opening or through passage port 446. In the illustrated position of the sleeve valve the channel 502, which communicates with the pressure conduit P14, is operatively connected via the annular groove 52 in flow relationship with the channel 501 which, in turn, communicates with the displacement piston member 22 possessing the larger effective cross-sectional area. The sleeve valve 4 is thus retained in the illustrated position. The outflow connection or conduit A13 is flow connected via the annular grooves 41 and 141 with the return flow conduit R12.

If the control sleeve valve 5 is pneumatically or hydraulically displaced toward the right, then the channels 501 and 502 are cutoff from one another, and the channel 501 is operatively connected with the return flow conduit R12 through the agency of the return flow channel 503 and the annular groove 51. The relieved displacement piston member 22 is pushed back, by the sleeve valve 4 within its associated bore 20 until it moves towards the left and comes into contact with the slide valve housing, and the sleeve valve 4 has been moved by the forces produced in the axial bore 430 through the action of the pressure of the fluid medium prevailing in the pressure line P. In so doing, the output connection or conduit A13 is separated or cut off from the return flow conduit R12 and is coupled or communicated in the annular grooves 11, 42 and 142 with the pressure conduit P14.

Escaping pneumatic or hydraulic leakage medium which has collected in the main bore or compartment to the left ,and/or right of the sleeve valve 4, is returned back to the return flow conduit R12 through the agency of three bores or channels 400 provided at the sleeve valve 4, as best illustrated in FIG. 4. The slide valve arrangement thus always remains operational. Finally, the channel means 18 communicate both of the enlarged compartments or chambers 16 and 17 with one another and towards the outside, therefore render possible, even during escape of leakage fluid medium in the enlarged widened compartments 16 and 17, a distrubance-free functioning of the membranes or diaphragms 120 and 130, respectively.

It should be apparent from the foregoing detailed description, that the objects set forth at the outset to the specification have been successfully achieved.

I claim:

1. A fluid-operated, in particular hydraulically or pneumatically controllable slide valve arrangement for alternately communicating in flow relationship an outflow conduit with a pressure conduit and return flow conduit of a fluid-operating system, comprising a slide valve housing provided with an outflow conduit, a pressure conduit and a return flow conduit, a sleeve valve member having opposed end faces, a respective coaxially extending displacement piston member acting upon each end face of said sleeve valve member, the effective crosssectional area of both of said displacement piston members differing from one another and being considerably smaller than the cross-sectional area of said sleeve valve member, fluid-operated control circuit means for continually applying a predetermined control pressure of a fluid medium to said displacement piston member possessing the smaller effective cross-sectional area and for alternately selectively applying the control pressure of the fluid medium of said control circuit means and a considerably smaller pressure to the other displacement piston member possessing the larger effective cross-sectional area.

2. A fluid-operated, in particular a hydraulically or pneumatically controllable slide valve arrangement as defined in claim 1, wherein said slide valve housing includes a lengthwise extending bore slidably receiving said sleeve valve member, discharge means for leakage fluid medium, said sleeve valve member being provided with at least one internal bore means for communicating the regions of said lengthwise extending bore located in front of said end faces of said sleeve valve member with said discharge means for said leakage fluid medi- 3. A fluid-operated, in particular a hydraulically or pneumatically controllable slide valve arrangement as defined in claim 1, further including an additional sleeve valve constructed as a slide valve provided at said slide valve housing, said additional sleeve valve serving for alternately operatively connecting said sleeve valve member with the pressure conduit of the fluid-operating system and for disconnecting therefrom, said additional sleeve valve having opposite situated end faces, a respective membrane cooperating with each end face of said additional sleeve valve for reciprocating the latter to and fro each of said membranes possessing an external face, respective control connection means neighboring said external face of each associated membrane and capable of being alternately subjected to an overpressure through the action of pneumatic or hydraulic control elements.

4. A fluid-operated, in particular a hydraulically or pneumatically controllable slide valve arrangement as defined in claim 3, further including means providing a respective compartment between each end face of said additional sleeve valve and its associated membrane, and discharge channel means for escaping fluid medium communicating with said respective compartments.

5. A fluid-operated, in particular hydraulically or pneumatically controllable slide valve arrangement for alternately communicating in flow relationship an outflow conduit with a pressure conduit and return flow conduit of a fluid-operating system, comprising a slide valve housing provided with an outflow conduit, a pressure conduit and a return flow conduit, a sleeve valve member having opposed end faces, a respective coaxially extending displacement piston member acting upon each end face of said sleeve valve member, the effective crosssectional area of both of said displacement piston members differing from one another, fluid-operated control circuit means for continually applying a predetermined control pressure of a fluid medium to said displacement piston member possessing the smaller effective cross-sectional area and for alternately selectively applying the control pressure of the fluid medium of said control. circuit means and a considerably smaller pressure to the other displacement piston member possessing the larger effective cross-sectional area, said slide valve housing incorporating cover means, said sleeve valve member having a bore, said displacement piston member possessing the smaller effective cross-sectional area and continually subjected to said control pressure being disposed in said bore and being impacted by said control pressure in the same direction as said displacement piston member possessing the larger effective cross-sectional area, said displacement piston member of smaller cross-sectional area bearing against said cover means, said sleeve valve member pushing against said displacement piston member possessing the smaller effective cross-sectional area as soon as the other displacement piston member of larger cross-sectional area is no longer subjected to the action of the control pressure.

6. A fluid-operated, in particular hydraulically or pneumatically controllable slide valve arrangement for alternately communicating in flow relationship an outflow conduit with a pressure conduit and return flow conduit of a fluid-operating system, comprising a slide valve housing provided with an outflow conduit, a pressure conduit and a return flow conduit, a sleeve valve member having opposed end faces, a respective coaxially extending displacement piston member acting upon each end face of said sleeve member, the effective cross-sectional area of both of said displacement piston members differing from one another, fluid-operated control circuit means for continually applying a predetermined control pressure of a fluid medium to said displacement piston member possessing the smaller effective cross-sectional area and for alternately selectively applying the control pressure of the fluid medium of said control circuit means and a considerably smaller pressure to the other displacement piston member possessing the larger effective cross-sectional area, an additional sleeve valve constructed as a slide valve provided at said slide valve housing, said additional sleeve valve serving for alternately operatively connecting said sleeve valve member with the pressure conduit of the fluid-operating system and for disconnecting therefromysaid additional sleeve valve having opposite situated end faces, a respective membrane cooperating with each end face of said additional sleeve valve for reciprocating the latter to and fro, each of said membranes possessing an external face, respective control connection means neighboring said external face of each associated membrane and capable of being alternately subjected to an overpressure through the action of pneumatic or hydraulic control elements, means providing a respective compartment between each end face of said additional sleeve valve and its associated membrane, discharge channel means for escaping fluid medium communicating with said respective compartments, said slide valve housing incorporating cover means, said sleeve valve member having a bore, said displacement piston member possessing the smaller effective cross-sectional area and continually subjected to said control pressure being disposed in said bore and being impacted by said control pressure in the same direction as said displacement piston member possessing the larger effective cross-sectional area, said displacement piston member of smaller cross-sectional area bearing against said cover means, said sleeve valve member pushing against said displacement piston member possessing the smaller effective cross-sectional area as soon as the other displacement piston member of larger cross section area is no longer subjected to the action of the control pressure.

7. A fluid-operated, in particular hydraulically or pneumatically controllable slide valve arrangement for alternately communicati'ng in flow relationship an outflow conduit with a pressure conduit and return flow conduit of a fluid-operating system, comprising a slide valve housing provided with an outflow conduit, a pressure conduit and a return flow conduit, a sleeve valve member having opposed end faces, a respective coaxially extending displacement piston member acting upon each end face of said sleeve valve member, the effective crosssectional area of both of said displacement piston members differing from one another, fluid-operated control circuit means for continually applying a predetermined control pressure of a fluid medium to said displacement piston member possessing the smaller effective cross-sectional area and for alternately selectively applying the control pressure of the fluid medium of said control circuit means and a considerably smaller pressure to the other displacement piston member possessing the larger effective cross-sectional area. an additional sleeve valve constructed as a slide valve provided at said slide valve housing, said additional sleeve valve serving for alternately operatively connecting said sleeve valve member with the pressure conduit of the fluid-operating system and for disconnecting therefrom, said additional sleeve valve having opposite situated end faces, a respective membrane cooperating with each end face of said additional sleeve valve for reciprocating the latter to and fro each of said membranes possessing an external face, respective control connection means neighboring said external face of each associated membrane and capable of being alternately subjected to an overpressure through the action of pneumatic or hydraulic control elements, said slide valve housing incorporating cover means, said sleeve valve member having a bore, said displacement piston member possessing the smaller effective cross-sectional area and continually subjected to said control pressure being disposed in said bore and being impacted by said control pressure in the same direction as said displacement piston member possessing the larger effective cross-sectional area, said displacement piston member of smaller cross-sectional area bearing against said cover means, said sleeve valve member pushing against said displacement piston member possessing the smaller effective cross-sectional area as soon as the other displacement piston member of larger cross-sectional area is no longer subjected to the action of the control pressure. 

1. A fluid-operated, in particular hydraulically or pneumatically controllable slide valve arrangement for alternately communicating in flow relationship an outflow conduit with a pressure conduit and return flow conduit of a fluidoperating system, comprising a slide valve housing provided with an outflow conduit, a pressure conduit and a return flow conduit, a sleeve valve member having opposed end faces, a respective coaxially extending displacement piston member acting upon each end face of said sleeve valve member, the effective crosssectional area of both of said displacement piston members differing from one another and being considerably smaller than the cross-sectional area of said sleeve valve member, fluidoperated control circuit means for continually applying a predetermined control pressure of a fluid medium to said displacement piston member possessing the smaller effective cross-sectional area and for alternately selectively applying the control pressure of the fluid medium of said control circuit means and a considerably smaller pressure to the other displacement piston member possessing the larger effective crosssectional area.
 2. A fluid-operated, in particular a hydraulically or pneumatically controllable slide valve arrangement as defined in claim 1, wherein said slide valve housing includes a lengthwise extending bore slidably receiving said sleeve valve member, discharge means for leakage fluid medium, said sleeve valve member being provided with at least one internal bore means for communicating the regions of said lengthwise extending bore located in front of said end faces of said sleeve valve member with said discharge means for said leakage fluid medium.
 3. A fluid-operated, in particular a hydraulically or pneumatically controllable slide valve arrangement as defined in claim 1, further including an additional sleeve valve constructed as a slide valve provided at said slide valve housing, said additional sleeve valve serving for alternately operatively connecting said sleeve valve member with the pressure conduit of the fluid-operating system and for disconnecting therefrom, said additional sleeve valve having opposite situated end faces, a respective membrane cooperating with each end face of said additional sleeve valve for reciprocating the latter to and fro each of said membranes possessing an external face, respective control connection means neighboring said external face of each associated membrane and capable of being alternately subjected to an overpressure through the action of pneumatic or hydraulic control elements.
 4. A fluid-operated, in particular a hydraulically or pneumatically controllable slide valve arrangement as defined in claim 3, further including means providing a respective compartment between each end face of said additional sleeve valve and its associated membrane, and discharge channel means for escaping fluid medium communicating with said respective compartments.
 5. A fluid-operated, in particular hydraulically or pneumatically controllable slide valve arrangement for alternately communicating in flow relationship an outflow conduit with a pressure conduit and return flow conduit of a fluid-operating system, comprising a slide valve housing provided with an outflow conduit, a pressure conduit and a return flow conduit, a sleeve valve member having opposed end faces, a respective coaxially extending displacement piston member acting upon each end face of said sleeve valve member, the effective cross-sectional area of both of said displacement piston members differing from one another, fluid-operated control circuit means for continually applying a predetermined control pressure of a fluid medium to said displacement piston member possessing the smaller effective cross-sectional area and for alternately selectively applying the control pressure of the fluid medium of said control circuit means and a considerably smaller pressure to the other displacement piston member possessing the larger effective cross-sectional area, said slide valve housing incorporating cover means, said sleeve valve member having a bore, said displacement piston member possessing the smaller effective cross-sectional area and continually subjected to said control pressure being disposed in said bore and being impacted by said control pressure in the same direction as said displacement piston member possessing the larger effective cross-sectional area, said displacement piston member of smaller cross-sectional area bearing against said cover means, said sleeve valve member pushing against said displacement piston member possessing the smaller effective cross-sectional area as soon as the other displacement piston member of larger cross-sectional area is no longer subjected to the action of the control pressure.
 6. A fluid-operated, in particular hydraulically or pneumatically controllable slide valve arrangement for alternately communicating in flow relationship an outflow conduit with a pressure conduit and return flow conduit of a fluid-operating system, comprising a slide valve housing provided with an outflow conduit, a pressure conduit and a return flow conduit, a sleeve valve member having opposed end faces, a respective coaxially extending displacement piston member acting upon each end face of said sleeve member, the effective cross-sectional area of both of said displacement piston members differing from one another, fluid-operated control circuit means for continually applying a predetermined control pressure of a fluid medium to said displacement piston member possessing the smaller effective cross-sectional area and for alternately selectively applying the control pressure of the fluid medium of said control circuit means and a considerably smaller pressure to the other displacement piston member possessing the larger effective cross-sectional area, an additional sleeve valve constructed as a slide valve provided at said slide valve housing, said additional sleeve valve serving for alternately operatively connecting said sleeve valve member with the pressure conduit of the fluid-operating system and for disconnecting therefrom, said additional sleeve valve having opposite situated end faces, a respective membrane cooperating with each end face of said additional sleeve valve for reciprocating the latter to and fro, each of said membranes possessing an external face, respective control connection means neighboring said external face of each associated membrane and capable of being alternately subjected to an overpressure through the action of pneumatic or hydraulic control elements, means providing a respective compartment between each end face of said additional sleeve valve and its associated membrane, discharge channel means for escaping fluid medium communicating with said respective compartments, said slide valve housing incorporating cover means, said sleeve valve member having a bore, said displacement piston member possessing the smaller effective cross-sectional area and continually subjected to said control pressure being disposed in said bore and being impacted by said control pressure in the same direction as said displacement piston member possessing the larger effective cross-sectional area, said displacement piston member of smaller cross-sectional area bearing against said cover means, said sleeve valve member pushing against said displacement piston member possessing the smaller effective cross-sectional area as soon as the other displacement piston member of larger cross section area is no longer subjected to the action of the control pressure.
 7. A fluid-operated, in particular hydraulically or pneumatically controllable slide valve arrangement for alternateLy communicating in flow relationship an outflow conduit with a pressure conduit and return flow conduit of a fluid-operating system, comprising a slide valve housing provided with an outflow conduit, a pressure conduit and a return flow conduit, a sleeve valve member having opposed end faces, a respective coaxially extending displacement piston member acting upon each end face of said sleeve valve member, the effective cross-sectional area of both of said displacement piston members differing from one another, fluid-operated control circuit means for continually applying a predetermined control pressure of a fluid medium to said displacement piston member possessing the smaller effective cross-sectional area and for alternately selectively applying the control pressure of the fluid medium of said control circuit means and a considerably smaller pressure to the other displacement piston member possessing the larger effective cross-sectional area, an additional sleeve valve constructed as a slide valve provided at said slide valve housing, said additional sleeve valve serving for alternately operatively connecting said sleeve valve member with the pressure conduit of the fluid-operating system and for disconnecting therefrom, said additional sleeve valve having opposite situated end faces, a respective membrane cooperating with each end face of said additional sleeve valve for reciprocating the latter to and fro each of said membranes possessing an external face, respective control connection means neighboring said external face of each associated membrane and capable of being alternately subjected to an overpressure through the action of pneumatic or hydraulic control elements, said slide valve housing incorporating cover means, said sleeve valve member having a bore, said displacement piston member possessing the smaller effective cross-sectional area and continually subjected to said control pressure being disposed in said bore and being impacted by said control pressure in the same direction as said displacement piston member possessing the larger effective cross-sectional area, said displacement piston member of smaller cross-sectional area bearing against said cover means, said sleeve valve member pushing against said displacement piston member possessing the smaller effective cross-sectional area as soon as the other displacement piston member of larger cross-sectional area is no longer subjected to the action of the control pressure. 